diff --git a/features/keychain/api/index.d.ts b/features/keychain/api/index.d.ts
index 31ed482..52f5523 100644
--- a/features/keychain/api/index.d.ts
+++ b/features/keychain/api/index.d.ts
@@ -36,7 +36,9 @@ export interface KeychainApi {
   secp256k1: {
     signBuffer(params: { data: Buffer } & KeySource): Promise<Buffer>
     signBuffer(params: { data: Buffer; enc: 'der' } & KeySource): Promise<Buffer>
-    signSchnorr(params: { data: Buffer; extraEntropy?: Buffer } & KeySource): Promise<Buffer>
+    signSchnorr(
+      params: { data: Buffer; extraEntropy?: Buffer; tweak?: Buffer } & KeySource
+    ): Promise<Buffer>
   }
 }
 
diff --git a/features/keychain/module/crypto/secp256k1.js b/features/keychain/module/crypto/secp256k1.js
index 36c53ad..060108f 100644
--- a/features/keychain/module/crypto/secp256k1.js
+++ b/features/keychain/module/crypto/secp256k1.js
@@ -49,7 +49,7 @@ export const create = ({ getPrivateHDKey }) => {
       )
       const hdkey = getPrivateHDKey({ seedId, keyId })
       const privateKey = tweak ? tweakPrivateKey({ hdkey, tweak }) : hdkey.privateKey
-      return Buffer.from(await secp256k1.schnorrSign({ data, privateKey, extraEntropy }))
+      return secp256k1.schnorrSign({ data, privateKey, extraEntropy, format: 'buffer' })
     },
   })